Wastepaper has long served as a source of the raw fiber materials used in papermaking. Traditionally, fiber from wastepaper was utilized only in the production of low grade paper and paperboard products. Today, however, greater utilization of reclaimed fiber has provided incentive for taking steps to upgrade the reclaimed product. These steps include treatment to effectively remove ink from waste fibers in order to permit their use in the manufacture of newsprint and high quality papers. Increasing amounts of office waste paper are becoming available. Because of the high quality cellulose fiber in office waste paper, efficient ink removal is particularly desirable since excellent quality, high value products can be prepared from this deinked pulp.
In the course of the conventional paper reclamation process of interest, deinking procedures include steps for converting the wastepaper to pulp and contacting the pulp with an alkaline aqueous deinking medium containing a chemical deinking agent. The physical pulping and the alkalinity of the aqueous medium cause the partial removal of ink from the pulp fiber and the deinking agent completes this removal and produces an aqueous suspension and/or dispersion of the ink particles thus removed from the pulp. The resulting mixture is subsequently treated to separate the suspended ink from the pulp.
A variety of materials, particularly surfactants and mixtures of surfactants are known to be useful as deinking agents in such a process, at least when the process is applied to the deinking of such common wastepaperstocks as newsprint, book, magazine and ledger. It is recognized, however, that conventional processes have not been particularly successful in specific application to xerographically printed wastepapers and laser printer wastepapers. The difficulty encountered in the deinking of these wastepapers has been attributed to the character of electrostatic ink, specifically to binder, which is fundamentally different from that used in other printing processes. For example, in distinction to the common oil or resin binders of other inks, the electrostatic ink binder is typically a polymeric material (e.g., polyethylene) which during the printing process is fixed to the paper by application of heat.
The ever-increasing utilization of xerographic and laser printed paper has made reclamation of office wastepaper containing xerographically printed paper economically attractive. Accordingly, the object of the present invention is a deinking process which is effective in the treatment of office wastepaper stock. As used herein, "office wastepaper" refers to xerographically printed stocks which may contain other materials such as laser printed stocks and ledger stocks.
The present invention centers on the use in a deinking process of a chemical deinking agent which is a detergent-range (e.g., C.sub.8 to C.sub.18) fatty alcohol. It is known in the art that the removal of ink from wastepaper can be accomplished by a process in which the paper is reduced to pulp and the pulp is contacted with an aqueous medium containing a surfactant as a deinking agent. For example, it is known from U.S. Pat. No. 4,561,933, that xerographically printed wastepaper can be deinked using a mixture of one or more C.sub.5 to C.sub.20 alkanols and nonionic surfactant. It is also known in the paper deinking art (for example, U.S. Pat. No. 4,162,186) to employ chemical agents which are ethylene oxide adducts ("ethoxylates") of detergent-range alcohols or alkyl-substituted phenols containing an average of about 7 to about 15 oxyethylene units per molecule of alcohol. It is further known from U.S. Pat. No. 4,518,459 to use surfactants for deinking which are hydroxy-terminated or benzyl ether-terminated ethylene oxide-propylene oxide adducts (ethoxypropoxylates) of high molecular weight or long chain alcohols.
It has now been found that certain fatty alcohols are very usefully applied as deinking agents in process for the deinking of office wastepaper. Processes applying fatty alcohol deinking agents are found to offer a high level of performance from the standpoint of the overall brightness of papers prepared from the deinked pulp. In addition, the invention provides for low foaming and high biodegradability without adverse influence upon deinking performance and reclaimed paper product brightness.